Corrosion behaviors of CrNx and (Ti1-xCrx)N coatings produced by ion plating

The corrosion behavior of CrNx and (Ti1-xCrx)N coatings, produced by reacti ve ion plating using thermal and electron beam evaporation, was investigate d. To deposit the CrNx coatings, Cr was evaporated by resistance heating an d CrNx coatings of various N/Cr composition ratios were obtained by alterin g the NH3 flow rate. For deposition of the (Ti1-xCrx)N coatings, Ti and Cr were evaporated by electron beam and resistant heating, respectively. The T i and Cr concentrations were controlled by the Ti to Cr evaporation ratio. Electrochemical properties of the coatings were examined with an EG&G 273 A potentiostat in a pH 7, 0.9 M NaCl solution. The corrosion behavior of bot h CrN and (Ti,Cr)N coatings showed a similar trend to that of pure Cr. At v oltages <0.5 V [versus saturated calomel electrode (SCE)], they showed pass ivity. However, at voltages >0.5 V (versus SCE), the corrosion current incr eased abruptly with dissolution of Cr-oxide from the surface oxide layer. ( C) 2001 American Vacuum Society.